Cabazitaxel, chemically known as 4-acetoxy-2α-benzoyloxy-5β,20-epoxy-1-hydroxy-7β,10β-dimethoxy-9-oxotax-11-en-13α-yl(2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenyl-propionate, is represented by formula (I).

It is a microtubule inhibitor, indicated in combination with prednisone for treatment of patients with hormone-refractory metastatic prostate cancer previously treated with a docetaxel-containing treatment regimen, under the trade name Jevtana®.
Cabazitaxel is known from U.S. Pat. No. 5,847,170. The process for the preparation of cabazitaxel as described in U.S. Pat. No. 5,847,170 involves column chromatography, which is cumbersome, tedious and not commercially viable.
The acetone solvate of 4-acetoxy-2α-benzoyloxy-5β,20-epoxy-1-hydroxy-7β,10β-dimethoxy-9-oxotax-11-en-13α-yl(2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenyl-propionate (Form A) is formed by crystallization by using acetone and is characterized by X-ray diffraction in U.S. Pat. No. 7,241,907.
U.S. Patent Application Publication No. 2011/0144362 describes anhydrous crystalline Forms B to Form F, ethanolates Form B, D, E and F and mono and dihydrate forms of cabazitaxel. All of the anhydrous crystalline forms are prepared either from the acetone solvate or ethanol solvate. Mono and dihydrate forms are formed at ambient temperature in an atmosphere containing 10% and 60% relative humidity, respectively.
From the above mentioned references, it is evident that pure polymorphic forms of cabazitaxel prepared in the literature were prepared from solvates and not directly from cabazitaxel.
None of the literature reported earlier mentions the amorphous form of cabazitaxel. The present invention provides a novel form of cabazitaxel, i.e., amorphous cabazitaxel which is directly obtained from crude 1 cabazitaxel without formation of any solvate or hydrate of cabazitaxel.